JPH0535112B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a heat insulator which is particularly susceptible to handling damage by applying a protective jacket to the surface of a block of microporous heat insulating material.

Conventional configurations and their problems Generally, they contain silica-aerogel particles with a small particle size on the order of 0.1 μm or less, an opacifying agent such as titanium oxide, and a fiber reinforcement, and are hardened to form a block. Microporous insulation materials are known.

This block has a bulk density of approximately 240 kg/m ³ and has better insulation properties than still air. However, although hard, it is brittle and is often covered with a fiberglass bag, for example, to protect it from damage from normal handling.

As the required shape becomes more complex, it becomes difficult to form encased blocks of glass fiber or the like.

Another known insulating material has a similar composition to the one mentioned above, but with a binder mixed in and a bulk density of 300-400 Kg/m ³
And a little big. As a result, the solidity of blocks formed from them is relatively less brittle. However, since the amount of binder is always kept to a minimum in order to minimize loss of insulating properties, the problem still arises that the surface layer will stick to the hand even with a light touch, and will break with a slightly stronger impact.

Purpose of the Invention As mentioned above, conventional insulation blocks are fragile, so the surface layer peels off and becomes dust, impairing workability, or is damaged during handling, resulting in gaps between the insulation block and the object to be insulated. For problems such as being able to
Although this type of microporous heat-insulating material has excellent heat-insulating properties, its use has been slow to expand. In particular, it has been difficult to use the heat insulating material with its surface exposed.

Therefore, in the present invention, the brittleness of the microporous heat insulating material is improved, the mechanical strength, especially the mechanical impact strength, of the film formed on the surface of the block of the microporous heat insulating material is improved, and the material is made easier to handle. The purpose is to provide a heat insulator that can be used without protecting the surface.

Structure of the Invention The heat insulating body of the present invention is obtained by applying a dense film of glaze containing a fibrous substance to the surface of a block of microporous heat insulating material.

The practical value of the present invention is particularly high when the microporous heat insulating material is a block obtained by mixing and compressing silica airgel particles, fiber reinforcing material and opacifying agent.

This is because the above-mentioned heat-insulating materials have better heat-insulating properties than still air.

Alternatively, it may be a heat insulating material having the above composition mixed with a binder.

The continuous heat resistance temperature of the above-mentioned heat insulating material mainly composed of silica airgel particles is about 950°C. Prolonged exposure to temperatures above this temperature will cause sintering and shrinkage, resulting in poor insulation properties.

Therefore, the glaze should be fired at a temperature below 950°C.
The glaze is made by adding a suspending agent such as clay or bentonite, a pigment, and water to a mixture of glass frit, silica, lime, borax, etc., which is fired to form a glass layer, and then crushed and mixed. The raw materials for the glaze must be selected so that it can be fired at temperatures below 950℃.

Further, since the heat insulating material is microporous, the coefficient of thermal expansion is small. Therefore, in order to prevent the glaze layer from peeling or cracking after firing, it is preferable to match the coefficient of thermal expansion of the glaze to that of the heat insulating material. However, because the insulation material is also microporous, some stress will be absorbed. Therefore, the allowable range for the coefficient of thermal expansion of glazes is relatively wide.

The glaze is applied to the surface of the insulation material by spraying, dipping, brushing, etc. After drying, the insulation is baked at a firing temperature for several minutes to several tens of minutes to complete the insulation.

The thickness of the glaze is determined from 100 mm to 100 mm depending on prevention of dripping during glazing, adhesion strength with the insulation material, and mechanical strength of the layer.
300 μm is preferred. Because the glaze layer is thin like this,
It does not adversely affect insulation performance.

This glaze layer is mechanically bonded to the micropores of the heat insulating material, and also contains highly active silica particles due to its fine particles.
The airgel and glaze components diffuse into each other and chemically bond, resulting in strong adhesion.

In addition, the glaze is made of glass fiber and aluminum.
Since short fibers or whiskers such as silicate fibers, short metal fibers, silicon carbide whiskers, or silicon nitride whiskers are mixed in a few to 10% and baked, the strength of the glaze film and the heat insulator is further improved.

DESCRIPTION OF THE EMBODIMENTS The microporous insulation material consists primarily of silica airgel particles with relatively small amounts of opacifier and fiber reinforcement. A preferred opacifying agent is titanium dioxide;
The preferred reinforcement is alumino-silicate fiber. Typical compositions follow the preferred criteria below, with the most preferred ranges shown in brackets.

Weight % Silica-airgel 50-97 (60-73) Reinforcement fiber 1-10 (2-7) Opacifier 2-40 (25-40) A particularly preferred composition is 63% by weight silica-airgel particles, 32% by weight Rutile (opacifier) and 5
% alumino-silicate fibers by weight. Suitable airgel particles are available from Nippon Aerosil Co., Ltd.
It is commercially available under the trademark AEROSIL.

The above-mentioned heat insulating material has a bulk density of 200 to 400 Kg/m ³ . From the viewpoint of mechanical strength and heat insulation properties, the block is preferably 300 to 350 kg/m ³ .

For example, the glaze composition is as follows.

Glass frit 100 parts by weight Clay 4 Colloidal silica 1 Sodium aluminate 0.2 Sodium nitrite 0.1 Water 45 parts by volume The composition of the glass frit is: SiO ₂ 43% by weight B ₂ O ₃ 14 Na ₂ O 11 K ₂ O 9 〃 Al ₂ O ₃ 0.7 〃 Li ₂ O 0.3 〃 ZnO 1.0 〃 TiO ₂ 18 〃 F ₂ 2.5 〃 P ₂ O ₅ 0.5 〃. Furthermore, in order to increase the strength of the film formed with the glaze, 2 to 10 parts by weight of alumino-silicate fibers, short stainless steel fibers, silicon carbide whiskers, or silicon nitride whiskers are mixed into the glaze formulation.

Mix and grind the formulation in a ball mill. Then, add 1 to 3 g of the residue from a 200 mesh (74 μm opening) sieve containing 50 c.c.
Adjust to 1500-3000 centipoise. This glaze is sprayed onto the surface of the block of insulation material.
The amount of glaze applied should be such that the film thickness after firing is 100 to 300 μm.

The glazed block is dried at 100-200°C for about 30 minutes and then fired at 800°C for 2-3 minutes.

By the method described above, a glossy, dense film of an opacifier can be applied to the surface of a block of microporous heat insulating material.

Furthermore, it can be colored by mixing pigments into the glaze formulation. Furthermore, patterns can be applied to the surface of the dense film by screen printing, transfer, etc.

Since the film described above is glassy, it starts to soften at a temperature 200 to 300°C lower than the normal firing temperature. Therefore, if the heat insulating material has sufficient heat insulation properties at 500 to 600 DEG C., a dense film 2 can be applied to the entire surface of the microporous heat insulating material block 1 as shown in FIG.

However, as shown in Fig. 2, a heating element 4 is installed inside the microporous insulation block 3, and the surrounding temperature is
When the temperature rises to about 900°C, it is possible to apply a dense film 5 only on the warm temperature side. Even in this case, if you handle it by the outside (the coated part), you can prevent damage to the insulation material, and since the outside is glazed, you can expect a decorative effect.

The heat resistance performance of the film depends on the softening temperature of the glass frit, and if the frit is selected appropriately, insulation performance of around 750°C is possible.

Effects of the Invention As described above, according to the present invention, since the film is formed using a glaze containing a fibrous substance, the mechanical strength of the film, particularly the impact strength, can be improved, and the mechanical strength of the heat insulating body can be improved. Strength can be further improved. As a result, dust pollution during work is eliminated, and damage due to handling is prevented, making it possible to fully demonstrate insulation performance superior to that of still air.

Furthermore, by applying a film to the entire surface, it is possible to obtain a heat insulating body whose heat insulating performance does not deteriorate due to moisture absorption.

Furthermore, in addition to sufficient film strength, the film can be colored or patterned, making it possible to obtain a heat insulator that can be used directly as a box without providing a protective cover.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the heat insulating body of the present invention, and FIG. 2 is a sectional view showing another embodiment of the heat insulating body of the present invention. 1, 3... Microporous heat insulating material block, 2, 5...
...Dense film of glaze, 4...Heating element.

Claims (1)

[Scope of Claims] 1. A heat insulating body in which a dense film of glaze containing a fibrous substance is applied to the surface of a block of microporous heat insulating material. 2. The heat insulating body according to claim 1, wherein the heat insulating material is a block obtained by mixing and compressing silica airgel particles, fiber reinforcing material, and an opacifying agent.